Method of plugging mine passages having water emanating therefrom

ABSTRACT

The present invention relates to a method of plugging a mine passage and the like, having water emanating therefrom wherein a particulated solid material is deposited in the passage to form an initially permeable plug therein. The particulated solid material is of a type which will react with the water as it flows through the plug thereby neutralizing the water and forming a water-insoluble precipitate therein. As the flow of water continues through the plug, the permeability of the plug is progressively reduced by the precipitate and the flow of water subsequently shut off.

ited States Patent Gardner et al.

[451 .lan. 18,1972

[54] METHOD or PLUGGHNG MINE PASSAGES HAVING WATER EMANATING THEREFROM [72] Inventors: Tommy R. Gardner; John A. Knox, both of Duncan, Okla.

[73] Assignee: The United States of America as represented by the Secretary of the Interior v [22] Filed: July 9, 1969 [21] Appl. No.: 840,494

[52] US. Cl ..6l/35, 61/1, 166/292 [51] Int. Cl. ..E01g 5/10, E2lf 15/00 [58] Field ofSearch ....6l/36, 35, l;166/292, 293,

[56] References Cited UNITED STATES PATENTS 4 16, 189 12/1889 Neukirch ..6l/36 2,065,512 12/1936 Cabnon 166/292 2,378,687 6/1945 Chamberlain ....6l/36 3,418,813 12/1968 Dillon ..6l/36X Primary ExaminerStephen J. Novosad Att0rney-Ernest S. Cohen and William S. Brown [57] ABSTRACT 4 Claims, No Drawings METHOD OF PLUGGING MINE PASSAGES HAVING WATER EMANATING TI-IEREFROM BACKGROUND OF THE INVENTION 1. Field of the Invention The prsentinvention relates to a method of plugging mine passages and the like having water emanating therefrom, and more particularly, but not by way of limitation, to a method of plugging a mine passage and the like having water emanating therefrom wherein a particulated solid material is deposited in said passage to form a plug thereof, said material being of a type which will react with the water to fonn an insoluble precipitate.

2. Description of the Prior Art In certain areas water emanating from either active or abandoned underground mines finds its way into streams and rivers. Because such mine water is usually acid from reacting with minerals and other materials contained within the mines, pollution of the streams and rivers results. Many processes have been proposed for purifying such acid mine water before it is allowed to enter the streams and rivers. However, these processes have generally proved to be economically unattractive in that the apparatus required is expensive to install and operate. In addition, since a given mine commonly includes many openings through which acid water can escape, collection of the water purification presents a substantial problem.

In addition, since abandoned mines are often the greatest sources of pollution, many methods of sealing the openings or passages in the mines have been proposed. While these methods have met with varying degrees of success, they require the placement of expensive cementitious or other plugging material in the passages or elaborate equipment to carry out, or both.

The present invention provides a method of plugging mine passages having water emanating therefrom wherein an inexpensive plugging material may be used and elaborate equipment is not required for carrying out the method.

SUMMARY OF THE INVENTION The present invention relates to a method of plugging a mine passage and the like, having water emanating therefrom which comprises depositing a quantity of particulated solid material in the mine passage so that an initially water-permeable plug is formed therein. The material used in forming the plug is of a type which will react with the water to form an insoluble precipitate within the plug thereby progressively reducing the permeability of the plug and subsequently shutting off the emanation of the water from said passage.

It is, therefore, a general object of the present invention to provide a method of plugging mine passages and the like having water emanating therefrom.

A further object of the present invention is the provision of a method of plugging mine passages having acidic water emanating therefrom wherein the passage is plugged with relatively'inexpensive particulated material.

Yet a further object of the present invention is the provision of a method of plugging mine passages having acidic water emanating therefrom wherein a passage may be efiectively plugged and the emanation of acidic water from the passage shut off without the necessity of employing elaborate apparatus.

Still a further object of the present invention is the provision of a method of plugging a mine passage wherein an initially permeable plug is placed in the passage which will progressively become impermeable while simultaneously removing acid and iron from the water flowing therethrough.

Other and further objects and advantages will be apparent from the following detailed description of presently preferred embodiments of the invention, given for the purpose of disclosure.

DESCRIPTION OF THE PREFERRED EMBODIMENTS It has been observed that when certain materials. such as limestone or dolomite, are contacted with the acidic water emanating from mines, a neutralization reaction takes place whereby an insoluble precipitate or sludge is formed. The applicants have discovered that when these materials are particulated to a certain fineness, deposited in a mine passage in the form of a plug of a predetermined length, and acidic water emanating from the passage allowed to flow through the plug, the acidic water flowing through the plug will be neutralized. Additionally, the applicants have found that as the acidic water flows through the plug and is neutralized thereby, the water-insoluble sludge or precipitate formed in the neutralization reaction will be deposited on the material within the plug. Furthermore, as the flow of acidic water continues through the plug, the permeability of the plug will be progressively reduced until the plug is sealed over its entire length thereby effectively shutting oh the flow of water.

The acidic water emanating from active and abandoned mines normally contains quantities of iron, sulfuric acid and sulfate compounds. When such water is reacted with limestone, dolomite or similar materials, neutralization of the acid occurs and certain reaction precipitates are formed depending on the particular composition of the water. Typically, the precipitates are comprised of iron oxides, hydrated ferric sulfate and calcium sulfate.

When acidic mine water is passed through a plug of particulated solid material according to the present invention, the precipitates formed will be deposited on the material thereby reducing the permeability of the plug. Thus, a plug of a proper type and size of particulated material deposited in a particular mine passage will bring about the neutralization of acidic water passing therethrough, and will progressively become impermeable thereby eventually shutting off the flow of water from the mine passage all together.

In practice of the present invention, a passage of a particular size and having a particular flow rate of acidic water emanating therefrom must be plugged with a particulated material of proper size and quantity. That is, the particulated material used in forming the plug must be of a size which will result in an initial plug permeability adequate to allow the passage of the total volume of water flowing from the mine passage. This will insure that channeling or washing away of the particulated material does not occur and that the precipitate or sludge formed is deposited uniformly throughout the length of the plug. Additionally, the plug must be of a length which will provide sufficient contact or retention time of the water within the plug to bring about neutralization of the water before it passes out of the plug. That is, sufficient contact time must be provided to treat the water for removal of iron, acid and a portion of the sulfate contained therein. Furthermore, the particulated material used to form the plug must be of a fineness which will be effectively sealed by the precipitate formed in the neutralization reaction.

For a particular size of mine passage having acidic water emanating therefrom of a particular composition and flow rate, the size and quantity of particulated material required to effectively plug the passage may be determined using standard laboratory and engineering techniques.

EXAMPLE A Laboratory tests were run to simulate the plugging of an actual mine passage having acidic water emanating therefrom. A mine passage having an average cross-sectional area of 50 square feet, and a flow of 30 gallons per minute of acidic mine water was assumed. The acidic water used in the laboratory tests had the following analysis which very closely followed the actual analysis of a sample of acidic mine water taken from mine 62-008 near Lost Creek, W. Va.

TABLE I Acidic Water Analysis Acidity as Total Dissolved Calcium Sulfate CaCO,, Iron Iron. ion ion milliliter: per m.p.l. m.p.l. Content m.p.l. pH

liter(m.p.l.) m.p.l.

A quantity of crushed limestone was obtained from the Greer Limestone Company, located at Greer, W. Va., (Greer i 3 Graded Limestone) having the following analysis:

TABLE 11 Screen Analysis of Greer No. l 3

Graded Limestone U.S. Standard sieve K=uLQlAAP were: p=viscosity of water-centipoises Q flow rate-milliliters/sec. L length over which pressure drop measuredcentimeters AP= pressure dropatmospheres A cross-sectional areasquare centimeters K penneabilitydarcies Using the above equation, the permeability of the modified Greer 013 limestone was calculated to be 210 darcies.

LENGTH OF PLUG REQUIRED For the mine passageway assumed above square feet in cross section), using modified Greer #13 particulated limestone having a permeability of 210 darcies, a water pressure drop of 2 p.s.i., and an acidic water flow rate of 30 gallons per minute, the length of plug required was calculated to be 29 feet using the above equation, rearranged as follows:

FLOW TESTS TO DETERMINE PLUGGING AND NEUTRALIZATION CHARACTERISTICS A flow test simulating the above-assumed conditions was anss athe ab w ussi m9d fiqir l 3,,particulated limestone and acidic water having the analysis given in table I to determine the plugging and water neutralizing characteristics of the limestone.

A portion of the modified Greer #l3limcstone was placed in a plexiglas tube having a diameter of 1 inch and a length of 6 inches. A constant acidic water head of 2 p.s.i. was maintained on the limestone with a column of acidic water 4 feet 7 inches high while allowing the acidic water to flow through the column. A valve was installed between the column and limestone to initially regulate the flow of acidic water at a rate simulating a fiow of 30 gallons per minute from a 50-squarefoot mine passage (90 e.e./hr.). The flow of water through the limestone, the pH and other characteristics of the treated water were determined at intervals throughout the duration of the test.

TABLE III.FLOW TEST OF ACIDIC WATER THROUGH GRADED LIMESTONE PLUG r Treated Alkalinity water as H001, Calcium Sulfate flow Treated milliliters Total Dissolved ion ion rate, water per liter iron, iron, content, content,

Elapsed time, hours cc./hr. pH (m.p.l.) m.p.l m.p.l. m.p.l. m.p.l.

All particles in a sample of the Greer No. 13 limestone passing a 40-mesh screen were removed, and the remaining limestone (modified Greer No. 13 limestone) used in the tests set forth below.

PERMEABILITY The permeability of the modified Greer No. 13 limestone was determined in the following manner:

A portion of the modified Greer No. limestone was The flow of acidic water through the plug was effectively shut off after approximately hours had elapsed. Thus, a plugfgritgdgf modified Greer 1 3 particulated limestone having a cross section of 50 square feet and a length of 29 feet would effectively neutralize and subsequently shut off 30 gallons per minute of acidic water emanating from a SO-squarefoot mine passage.

From table Ill above it may be seen that the plug formed of properly sized particulated limestone'effectively neutralized acidic mine water while the permeability of the plug was progressively reduced by the precipitation of sludge in the plug. It may also be seen that for a given mine passage having acidic water emanating therefrom, a plug of particulatcd material of the present invention may be deposited in the passage. Acidic water flowing through the plug after placement thereof will he neutralized so that the water may be allowed to flow into nearby streams and rivers without fear of pollution resulting therefrom. After an initial period of time the insoluble precipitate or sludge deposited in the plug as a result of the neutralization reaction will bring about the sealing of the plug over its entire length thereby effectively shutting off further flow of water from the mine passage.

EXAMPLE B The present invention was tested at an actual mine site (mine 40-085) near Mount Clare, W. Va.

Acidic water emanating from the mine passage was used for the test. A flume was constructed adjacent to the mine opening of a size corresponding with the mine passage. The flume was constructed from exterior grade plywood and had a crosssectional area of 30 square feet and a length of 30 feet. The flume was divided into three parallel sections running the length thereof, 2 feet wide and 5 feet high. The head of the flume was fitted with a sediment box which contained three valves to regulate the flow of acid mine water into each of the three sections.

Laboratory tests of the type described above indicated that a Type I2 limestone from the Harrold Limestone Company, Clarksburg, W. Va., could be used in the test. The screen analysis of the Harrold No. 12 limestone used is given in table IV.

TABLE IV Screen Analysis of I-Iarrold No. l2

Limestone U.S. Standard sieve Mesh size Passed Retained Percent iz' 1.25 5? 3 V: 28.41 3% 8 59.11 8 12.95 20 I00 1.48 I00 pan 0.7I

' Diameter of screen opening All three sections of the flume were packed with Harrold No. 12 limestone. In one section (section I) of the flume the acid mine water was placed in contact with the limestone near the bottom, approximately 6 inches off the floor by means of a 3-inch plastic pipe. In the center section (section II) of the flume the acid mine water was placed on top of the limestone bed at a point near the head of the flume. In the third section of the flume (section III), the acid mine water was distributed down the top of the limestone bed for a distance of 20 feet by means of a 2-inch plastic pipe having a plurality of holes drilled therein along the length thereof.

A flow rate of approximately 9.4 gallons per minute of acid mine water emanating from the mine passage was started through each of the three sections of the flume.

RESULTS The water flowing through all three sections of the flume was effectively neutralized by the I-Iarrold No. 12 limestone contained therein throughout the duration of the test. After an initial period of time, all three sections of limestone in the flume became substantially sealed due to the depositing of precipitate or sludge on the limestone.

Throughout the test the pH and acidity of the acid mine water flowing from mine 40-085 into the flume were determined. The results of these determinations are shown in table V. Also, the flow, pH and acidity of the water from each section of the flume were determined periodically throughout the test, and are shown in tables VI VII, and VIII.

Flow, pH and Acidity of Water from Section I of Flume Flow of water Acidity as from section I, CaCO gallons/minute milligrams Date pH per liter Dec. 20. I968 9.4 5.9 200 Dec. 24, I968 8.75 5.8 200 Jan. 2, I969 2.31 6.1 Jan. 6, I969 L63 Jan. 8, I969 0.7 6.3 10 .Ian. I3, I969 0.33 Jan. 15, I969 0.20 6.0 60

Section overflowed. The input pipe located near the bottom of the section was removed and the water placed in contact with the limestone at the top near the head of the flume.

Section over-flowed and flow rate of acid water to the section was adjusted.

TABLE VII Flow, pH, and Acidity of Water from Section II of Flume Flow of water Acidity as from section II, CaCO gallons/minute milligrams Date pH per liter Dec. 20, I968 9.4 6.1 IIO Dec. 24, 1968 7.5 5.9 I60 Dec. 3|, I968 2.25 Jan. 2, I969 L77 6.2 0 .Ian. 8, I969 0.20 6.3 0 Jan. l5, I969 0.25 6.2 0 Jan. 24, I969 0.24 6.6 I89 Jan. 27, 1969 0.06

' Section overflowed and flow rate of acid water to the section was adjusted.

TABLE VIII Flow, pH, and Acidity of Water from Section III of Flume Flow of water Acidity as from section III, CaCO gallons/minute milligrams Date pH per liter Dec. 20, I968 9.4 6.7 70 Dec. 24, I968 5.0 6.0 0 Jan. 2, I969 25 6.2 20 .Ian. 8, I969 0.60 6.2 0 Jan. l5, I969 3.75 5.7 200 Jan. 25, I969 0.25 6.6 I68 .Ian. 28, I969 0.Il

The flow of acid water to sectionsl and II had to be adjusted periodically throughout the test due to plugging of the portion of the limestone adjacent to the acid water inlet and plugging of the inlet valves.

From the above it may be seen that the acid water flowing through all three sections of the flume was neutralized by the limestone, and that the permeability of the limestone in all three sections was progressively reduced by the precipitation of sludge thereon.

Any particulated solid material may be employed in the present invention to seal a particular passage which has the property of reacting with the water emanating from the passage to form an insoluble precipitate. While most water emanating from active or abandoned mine passages is acidic, the present invention may be utilized to seal passages having neutral or alkaline water emanating therefrom through the use of a particulated solid material which will react with one or more components in the water to form a water-insoluble precipitate. Furthermore, it is not critical to the present invention that the particulated solid material employed bring about neutralization ofthe water.

The solid material employed in the present invention may be placed or deposited in a mine passage to be sealed in any convenient manner. For example, the plug of particulated material may be placed in the mouth or surface opening of a passage using conventional earth-moving equipment, or if the passage to be plugged is inaccessible from the ground surface, one or more bores may be drilled into the passage from the ground surface and the solid material deposited therethrough.

The present invention, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned,

as well as those inherent thercfin. While presently preferred embodiments of the invention are given for the purpose of disclosure, numerous changes will readily suggest themsclves to those skilled in the art and which are encompassed within the spirit of the invention disclosed herein.

What is claimed is:

l. A method of plugging mine passages and the like having acidic water emanating therefrom which comprises:

depositing a quantity of particulated solid material in said passage so that an initially water-permeable plug is formed therein, said material being of a type which will neutralize said acidic water as it flows through said plug while simultaneously forming an insoluble precipitate within said plug thereby progressively reducing the permeability of said plug and shutting off the flow of said water from said passage.

2. The method of claim 1 wherein said material is comprised of limestone.

3. The method of claim 1 wherein said material is comprised of dolomite.

4. A method of plugging mine passages and the like having acidic water emanating therefrom containing iron, acids, and sulfates which comprises:

depositing a quantity of particulated limestone in said passage so that a permeable plug thereof is formed therein; and

allowing said acidic water to flow through said plug so that said acidic water is neutralized and a precipitate comprised of iron oxides, hydrated ferric sulfate and calcium sulfate is formed within said plug thereby reducing the permeability of said plug and shutting off the flow of said water from said passage. 

2. The method of claim 1 wherein said material is comprised of limestone.
 3. The method of claim 1 wherein said material is comprised of dolomite.
 4. A method of plugging mine passages and the like having acidic water emanating therefrom containing iron, acids, and sulfates which comprises: depositing a quantity of particulated limestone in said passage so that a permeable plug thereof is formed therein; and allowing said acidic water to flow through said plug so that said acidic water is neutralized and a precipitate comprised of iron oxides, hydrated ferric sulfate and calcium sulfate is formed within said plug thereby reducing the permeability of said plug and shutting off the flow of said water from said passage. 